Over the past decade, substantial developments have been made in the micro-manipulation of fluids in fields such as electronic printing technology using inkjet printers. As the volume of fluid manipulated or ejected decreases the susceptibility to clogging of fluid channels and nozzles has increased. Fluid ejection cartridges provide a good example of the problems facing the practitioner in preventing the clogging of microfluidic channels and nozzles due to particulates.
Fluid ejection cartridges typically include a fluid reservoir that is fluidically coupled to a substrate that is attached to the back of a nozzle layer containing one or more nozzles through which fluid is ejected. The substrate normally contains an energy-generating element that generates the force necessary for ejecting the fluid held in the reservoir. Two widely used energy generating elements are thermal resistors and piezoelectric elements. The former rapidly heats a component in the fluid above its boiling point causing ejection of a drop of the fluid. The latter utilizes a voltage pulse to generate a compressive force on the fluid resulting in ejection of a drop of the fluid.
Currently there is a wide variety of highly-efficient inkjet printing systems in use, which are capable of dispensing ink in a rapid and accurate manner. However, there is a demand by consumers for ever-increasing improvements in speed and image quality. To improve image quality, the size or diameter of each nozzle typically decreases. For example, today printers generally have 300 to 600 dpi (dots per inch). In order to improve print speed the number of nozzles necessarily increases. Thus, improvements in both image quality and speed have led to a decrease in the size of the nozzles as well as an increase in the number of nozzles on a printhead. This utilization of a greater number of smaller nozzles has created a greater degree of susceptibility to plugging from particulates in the ink supply. The plugging of a nozzle results in serious degradation of the image or print quality of the printer system.
In order to prevent the nozzle system from becoming clogged with particulate matter, a mechanical filter element is typically disposed in the ink jet print cartridge such that the ink is filtered before it is supplied to the nozzle system. If the ink is not filtered it would tend to clog or block the nozzles. These mechanical filters are generally screens and typically made of stainless steel woven mesh. They are attached to what is generally referred to as a standpipe. The standpipe provides fluid communication between the ink reservoir of the print cartridge and the fluid ejectors. This mesh is typically rigidly secured around the edges to the standpipe to prevent leakage of ink around the filter element.
In addition, in an effort to reduce the cost and size of ink jet printers and to reduce the cost per printed page, printers have been developed having small, moving printheads that are connected to large stationary ink supplies. This development is called xe2x80x9coff-axisxe2x80x9d printing and has allowed the large ink supplies to be replaced as it is consumed without requiring the frequent replacement of the costly printhead containing the fluid ejectors and nozzle system. However, the typical xe2x80x9coff-axisxe2x80x9d system requires numerous flow restrictions between the ink supply and the printhead, such as additional orifices, long narrow conduits, and shut off valves. To overcome these flow restrictions and to also provide ink over a wide range of printing speeds, ink is now transported to the printhead at an elevated pressure. A pressure regulator is typically added to deliver the ink to the printhead at the optimum backpressure.
Further, an xe2x80x9coff-axisxe2x80x9d printing system strives to maintain the back pressure of the ink within the printhead to within as small a range as possible. Changes in back pressure greatly affect print density as well as print and image quality. In addition changes in back pressure can cause either the ink to drool out of the nozzles or to deprime the printhead. As consumer demands push the technology to ever smaller nozzles it becomes necessary to filter ever smaller particles from the ink. However, mechanical filter elements capable of filtering smaller particles typically require a larger pressure drop across the filter medium to generate the same flow rate as a larger particle filter. Thus, the requirement to filter smaller particles yet maintain the back pressure of the ink within the printhead to within as small a range as possible has produced a problem in inkjet technology development.
A fluid ejection cartridge includes a fluid container that has both a fluid inlet and a fluid outlet. The fluid ejection cartridge has one or more fluid ejectors fluidically coupled to the fluid container outlet and a fluid valve fluidically coupled to the fluid container inlet. The fluid ejection cartridge has a filter assembly having a compliant portion with an internal volume fluidically coupled to the fluid container outlet such that the internal volume changes when fluid flows into the fluid container.